You are confused about a lot of things.
MPPT is only useful when the load can accept the maximum power. This usually happens with solar battery chargers and grid-tie inverters. But if the load does not need the maximum power that the panel can produce, then you don't want to run MPPT. In that case, you want to select the duty cycle that produces the correct output voltage, regardless of the maximum power point.
Also, if the solar panel is not able to supply the power needed by the load (for example when the sun is going down or if the sun is obscured by clouds) then there is no way to maintain the output voltage that the load needs. You will have to shut down the load, or run the load at reduced voltage.
I think what you want is just a boost controller with a fixed output voltage, not an MPPT controller. If a cloud goes in front of the sun, or when the sun goes down, then you need to make sure your system handles this gracefully. Maybe you could have a small micronctroller that detects when this happens, and shuts down the load, then attempts to restart once every minute or once every hour, or whatever seems reasonable. It is not easy to say what is best without full knowledge of what you are trying to do.
The algorithm for an MPPT battery charger is just to try different PWM duty cycles in order to maximize battery charge current. You also need to monitor battery voltage and possibly battery temperature to avoid over-charge. There is more to it to have a safe system. That is just an outline.
